Float Zone Wafer – Characteristics and applications

• July 26, 2016
• WaferPro
• 0

Float zone (FZ) wafers, also known as perfect single crystal wafers, are an extremely pure form of single crystal silicon manufactured by WaferPro. They are produced using the float zone crystal growth method and have unique properties that make them suitable for demanding semiconductor and electronics applications.

This comprehensive guide covers everything you need to know about FZ wafers including their manufacturing process, properties, types, applications, specifications and why WaferPro is the foremost supplier for your float zone wafer requirements.

If you would like to buy high resistivity Float Zone Silicon Wafers, Check out our inventory and shop online here.

Table of Contents

• What are Float Zone Wafers?
• How Float Zone Wafers Are Manufactured
• Key Properties and Characteristics
• Applications and Uses
• WaferPro's Float Zone Wafer Specifications
• Types of Float Zone Wafers
• Ensuring Quality Control
• Customization Capabilities
• Benefits of Choosing WaferPro
• Research Applications
• Photovoltaic Applications
• Power Electronics Applications
• FAQs
• Summary - Float Zone Silicon Wafer Advantages

What are Float Zone Wafers?

Float zone wafers refer to semiconductor-grade monocrystalline silicon wafers manufactured using the float zone crystal growth technique. This specialized production method creates silicon wafers boasting exceptional quality and near perfect crystal properties unmatched by conventional ingot growth methods.

Some of the key attributes of float zone silicon wafers made by WaferPro include:

• Ultra-high purity - oxygen and carbon impurities under 1E14 atoms/cm3
• Essentially zero dislocation density - less than 1/cm2
• Highly uniform electrical resistivity
• Precisely controlled crystal orientations - within 0.1°
• Very low concentration of grown-in defects
• Low oxygen content for minimized thermal donors

These near-perfect crystal properties result from the float zone wafer production process and enable semiconductor devices and electronics with superior performance.

How are Float Zone Wafers Manufactured?

Float zone silicon wafers get their name from the specialized float zone crystal growth method used in their production. This technique relies on float zone melting to produce incredibly pure single crystal silicon ingots out of which wafers are sliced.

The float zone melting method works by focusing intense heating on a small molten region of a rotating polycrystalline silicon rod. As this hot zone traverses the length of the rod it leaves behind a solidified single crystal ingot up to 2000mm long.

Benefits of the Float Zone Growth Technique

The float zone wafer production process offers critical advantages:

• Ultra-High Purity - Only silicon melts avoiding impurities
• Precise Control - Tight regulation of vacancies and interstitials
• Axial Symmetry - Excellent uniformity along entire ingot length

This unrivaled growth technology allows the creation of extremely high quality float zone grade wafers boasting contamination levels and defect densities far below standard semiconductor wafers.

Key Properties and Characteristics of Float Zone Wafers

The specialized production process results in float zone wafers possessing a range of exceptional properties that enable high performance electronics and devices:

1. Ultra-High Purity

Primarily consisting of incredibly pure single crystal silicon thanks to no crucibles contacting the melt. Impurity levels down to ~1E12 atoms/cm3.

2. Virtually Dislocation Free

The lack of thermal gradients and slow solidification rate minimizes stresses. Dislocation densities <1/cm2 are standard.

3. Precisely Controlled Resistivity

Carefully regulating impurity atoms during growth allows uniform resistivities from 1 - 20,000+ ohm-cm.

4. Axial Symmetry

Minimal thermal gradients ensure impressive uniformity of FZ wafer properties along the entire wafer length.

5. Defect Free Surfaces

The elimination of dislocations results in ultra-smooth wafer surfaces with negligible defect densities.

These exceptional crystal properties enable the fabrication of high speed, high efficiency electronic devices. They are unmatched by conventional Czochralski-grown silicon wafers.

Applications and Uses of Float Zone Wafers

The superior quality and performance potential of float zone wafers make them the ideal choice for various advanced electronics applications:

High Efficiency Solar Cells

• Ultra-pure material with minimal defects boosts efficiency
• Enables conversion efficiencies exceeding 25%

Power Semiconductors & IGBTs

• Very high resistivity for high voltage power devices
• Low dislocations sustain large electric fields

Scientific Calibration Sensors

• Extremely precise lattice properties
• Sensitivities down to parts per million

Semiconductor Metrology Standards

• Near perfect crystal structure
• Ideal absolute reference material

Biomedical MEMS Devices

• High chemical resistance
• Meets biocompatibility standards

In summary, the unsurpassed quality of float zone wafers offer vast performance benefits for manufacturing everything from industrial power systems to precision sensors to renewable energy.

WaferPro's Float Zone Wafer Specifications

WaferPro offers an extensive range of float zone wafer sizes, orientations, resistivities, thicknesses and surface finishes to accommodate a wide span of application requirements.

Standard FZ Wafer Specifications:

• Diameters: 2”to 200mm
• Orientations: 100, 110, 111
• Resistivities: 1 to 20,000+ ohm-cm
• Thickness: 200-2000μm
• TTV: <5μm
• Surface: Polished or Etched

Our stringent production controls enable exceptionally tight tolerances on critical parameters like thermal donor concentration, oxygen precipitation density, thickness variation, resistivity uniformity and surface microroughness.

We also offer extensive customization capabilities to produce FZ wafers with specialized dimensions, flats, surface finishes or other properties needed for niche applications.

Ensuring Quality Control

Maintaining outstanding float zone wafer quality necessitates careful process monitoring and control from polycrystalline rod production through to final wafer preparation.

WaferPro utilizes the latest production technology combined with stringent quality control testing at every step:

• Raw material analysis
• Precise zone refining units
• Automated crystal growth systems
• Real-time monitoring
• Cross-sectional assessments
• Surface scans
• Resistivity mapping
• Microscopy inspection

This rigorous quality control ensures all our float zone silicon wafers exhibit extremely high and consistent standards.

Types of Float Zone Silicon Wafers

Wafer Type	Description	Applications
Standard	General purpose, polished surface, standard thickness and diameter	R&D, solar cells, sensors
High Resistivity	Tailored to specific high resistance >10,000 ohm-cm	High voltage devices, IGBTs
Custom Diameter	Diameters from 2” to 200mm	Specialty research, MEMS
Metrology Grade	Precisely calibrated for metrology standards	Calibration references
Epitaxy-Ready	Ultra-smooth surface < 2A RMS	Epitaxial depositions
Film Coated	With deposited thermal oxide, LPVCD nitride, or PECVD nitride layers	MEMS, biomedical
Diffusion-Doped	Custom thermal diffused layer	Power devices, PV

This table summarizes common categories of float zone (FZ) silicon wafers available from WaferPro including key applications each type is suited for based on custom electrical and physical attributes produced during the FZ manufacturing process.

Customization Capabilities

While we supply many standard float zone wafer products for common applications and research purposes, WaferPro also offers extensive customization capabilities.

Our specialized float zone process expertise and production technology allows tailored manufacturing of wafers to match precise specifications, including:

• Unique shapes and geometries
• Custom diameters and thickness
• Special flat or notch orientations
• Specific resistivity profiles
• Non-standard crystal orientations
• Customized surface finishes
• Application of specialty coatings
• Metrology grade calibration

Contact our engineering team to discuss producing specialized float zone wafers for your advanced application requirements.

Benefits of Choosing WaferPro

With over 8 years dedicated expertise manufacturing and supplying high quality float zone silicon wafers, WaferPro offers unique advantages:

Production Excellence

• Specialized only in float zone wafer manufacturing
• Continual investment in latest FZ production technology
• Highly refined manufacturing process controls
• Exceptional product consistency

Supply Reliability

• Extensive float zone wafer inventory
• Rapid fulfillment of standard items
• Prompt production of specialized orders
• Reliable on-time delivery

Application Experience

• Long history serving diverse electronics sectors
• In-depth understanding of application requirements
• Tailored FZ wafer specifications
• Technical consultation and expertise

Quality Assurance

• Stringent quality control procedures
• Precise monitoring and measurements
• Comprehensive wafer analysis data
• Total commitment to perfection

Our dedication to upholding rigorous float zone wafer quality standards and strong customer service makes WaferPro the premier choice for sourcing specialized float zone silicon.

Research Applications

The ultra-high quality and precise properties of float zone wafers are highly valued for scientific research applications in areas like:

Material Physics Research

The defined nature and purity simplifies analysis of fundamental physical properties. FZ wafers enable research into areas like:

• Thermal conductivity
• Silicon lattice dynamics
• Defect formation energies
• Optical characteristics

Electronic Characterization

The reproducible electrical characteristics facilitate research into topics including:

• Doping concentration analysis
• Charge carrier lifetimes
• Transport phenomenon
• Quantum effects

Metrology Calibrations

Nearly perfect FZ wafers serve as ideal reference standards for quantitative metrological research into parameters like:

• Surface quality
• Flatness/parallelism
• Deposition uniformity
• Etching precision
• Purity verification

Their exceptional quality makes float zone silicon wafers the ultimate base material for probing semiconductor physics phenomena and enabling characterization tool calibration.

Photovoltaic Applications

The ultra-high purity and minimal defects in float zone wafers offer vast advantages for fabricating extremely efficient high-performance solar cells.

Efficiency Enhancement

The negligible contamination and lack of dislocations in float zone silicon minimizes parasitic losses via recombination within the cell. This enables solar energy conversation efficiencies of 25-27% surpassing conventional materials.

Performance Benchmarking

FZ wafers serve as perfect reference substrates for evaluating new solar cell designs and fabrication processes without influence of material defects.

Specialized Devices

Custom FZ wafers with precisely engineered dopant profiles and thickness specifications can optimize absorption for niche PV applications like multi-junction tandem cells.

Ultimately the superior quality float zone wafers available from WaferPro help photovoltaic manufacturers push the boundaries of solar efficiency for renewable energy generation.

Power Electronics Applications

The high resistivities and low defect densities attainable with float zone wafers also provide vast advantages for manufacturing high voltage, high frequency power semiconductor devices.

IGBTs and Thyristors

The extreme purity and lack of dislocations allows very high resistance FZ silicon for fabrication of rectifiers, switches and power controllers sustaining voltages up to 10kV.

Power MOSFETs

FZ wafer enable creation of low capacitance high electron mobility transistors for efficient PWM converters operating at MHz frequencies.

Superjunction Devices

Precisely tailored FZ wafers featuring specialized doping profiles facilitate innovative superjunction device architectures boasting exceptional conductivity modulation.

Sensors and MEMS

FZ material possesses the stringent contamination control and crystal quality necessary for fabricating extremely sensitive inertial, pressure and gas sensors.

Mastering control over electrical properties during the float zone growth process permits tailoring wafers exactly suited to producing advanced power semiconductor devices pushing efficiency boundaries.

Frequently Asked Questions

Here we address some commonly asked questions regarding float zone wafers and WaferPro's products and services:

How much do float zone silicon wafers cost?

Due the high material purity and specialized production process, FZ wafers cost approximately 5-10x more than standard CZ wafers. However, considerable performance benefits often justify the price premium for advanced electronics.

What surface finishes are available?

Most often FZ wafers feature a polished surface but etched alternatives provide lower roughness. Dielectrically passivated surfaces are also possible.

What diameters of float zone wafers are manufactured?

WaferPro supplies float zone silicon wafers ranging from 2” specimens to 200mm production-scale wafers. Custom diameters are also possible.

Can you manufacture square or rectangular float zone wafers?

Yes, via precise sawing we can produce square, rectangular or other non-round float zone wafer geometries to customer specifications.

How long is your float zone wafer manufacturing lead time?

Standard polished inventory products ship immediately while processed custom orders ship in ~4 weeks. Fast 2 week expediting is available.

Summary - Float Zone Silicon Wafer Advantages

We hope this complete guide has provided beneficial details regarding the myriad advantages of float zone silicon wafers, their production, properties, applications and how WaferPro provides specialized float zone wafer solutions.

The key takeaways are:

• Exceptional Material Quality — Near intrinsic purity and negligible defects

• Optimized Electrical Properties — Ultra-precise resistivity control

• Axial Symmetry — Unmatched uniformity along wafer length

• Advanced Applications — Enable high-efficiency devices and precision metrology

• WaferPro Expertise — Specialized float zone wafer producer offering extensive customization

For further information on our available FZ wafer inventory, technical consultation, or customized products, please contact the WaferPro sales team to discuss how our float zone wafers can fulfill your application requirements.